Suppose you have a 100-watt light bulb that you leave
turned on for one minute. How much energy does it use?

Hint A.1

Study Section 5.1, and don't forget that
there are 60 seconds in 1 minute.

ANSWER:

6,000 joules 100 joules. 100
watts 6,000 watts

Part B

Suppose you are listening to a radio station that
broadcasts at a
frequency of 97 Mhz. Which of the following statements is true?

Hint B.1

Mhz stands for megahertz, which is a
million hertz. Review the definition of hertz in your text.

ANSWER:

The "radio waves" that are received by your radio are not light waves
like those we talk about in astronomy, but rather are a special type of
sound wave.
The radio waves from the radio station are causing electrons in your
radio's antenna to move up and down 97 million times each second. The
radio waves from the radio station have a wavelength of 97 million
meters. The radio station broadcasts its signal with a power of
97 million watts.

Part C

Gamma rays have a very small ______.

Hint C.1

Study Section 5.2.

ANSWER:

frequency. wavelength. mass. energy.

Part D

Suppose a photon has a frequency of 300 million hertz (300
megahertz). What is its wavelength?

Hint D.1

The speed of light is 300 million m/s.

ANSWER:

A photon's wavelength cannot be determined from its
frequency. 1 meter. 300 million meters.
1/300,000 meter.

Part E

Which of the following best describes why we say that light
is an electromagnetic wave?

Hint E.1

Study Section 5.2.

ANSWER:

Light is produced only when massive fields of electric
and magnetic energy collide with one another. Light can be
produced only by electric or magnetic appliances. The term
electromagnetic wave arose for historical reasons, but we now know
that light has nothing to do with either electricity or magnetism. The passage of a light wave can cause electrically
charged particles to move up and down.

Part F

Which of the following statements about X rays and radio
waves is NOT true?

Hint F.1

Study Section 5.2.

ANSWER:

X rays and radio waves are both forms of light, or
electromagnetic radiation. X rays have shorter wavelengths than
radio waves. X rays travel through space faster than
radio waves. X rays have higher frequency than radio waves.

Part G

Each of the following describes an "Atom 1" and an "Atom
2." In which case are the two atoms different isotopes
of the same element?

Suppose you had some molecular oxygen (O2)
chilled enough so that it was in liquid form. Which of the following
best describes the phase changes that would occur as you heated the
liquid oxygen up?

Hint H.1

Study Section 5.3

ANSWER:

The liquid molecules would quickly dissociate into a liquid of
individual oxygen atoms. These atoms would then evaporate into a gas,
and then become ionized to make a plasma.
It would evaporate into a gas, then the molecules would dissociate into
individual oxygen atoms, then the atoms would become increasingly
ionized as you continued to raise the temperature.
It would sublime into a gas, then the molecules would lose electrons
until no electrons were left, then the molecules would dissociate into
individual oxygen nuclei.
The cold temperature would first cause the oxygen to solidify. The
solid would then sublime into a gas, which would then become a plasma
as the molecules lost their electrons, until finally it consisted of
bonded pairs of oxygen nuclei stripped bare of any electrons.

Part I

Consider an atom of oxygen in which the nucleus contains 8
protons and 8 neutrons. If it is doubly ionized, what is the charge of
the oxygen ion and how many electrons remain in the ion?

Hint I.1

Study Section 5.3.

ANSWER:

Charge is +2; number of remaining electrons = 8. Charge
is --2; number of remaining electrons = 10.
Charge is +2; number of remaining electrons = 6. Charge is +2; number
of remaining electrons = 2.

Part J

Which of the following statements about electrons is
NOT true?

Hint J.1

Study Section 5.3

ANSWER:

Electrons orbit the nucleus rather like
planets orbiting the Sun.
Electrons can jump between energy levels in an atom only if they
receive or give up an amount of energy equal to the difference in
energy between the energy levels. Within an atom, an electron can have
only particular energies. Electrons have very little mass
compared to protons or neutrons. An electron has a negative electrical
charge.

Part K

Which of the following conditions lead you to see an
absorption
line spectrum from a cloud of gas in interstellar space?

Hint K.1

Study Section 5.4

ANSWER:

The cloud is cool and very dense, so that you cannot see
any objects that lie behind it. The cloud is extremely hot. The cloud is cool and lies between you and a hot
star. The cloud is visible primarily because it reflects light
from nearby stars.

Part L

The following diagram represents energy levels in a
hydrogen
atom. The labeled transitions (A through E) represent an electron
moving between energy levels.Which labeled transition represents an
electron that absorbs a photon with 10.2 eV of
energy?

Hint L.1

Study Section 5.3 and 5.4.

ANSWER:

B A C D

Part M

If an electron at level 1 in a hydrogen atom absorbs 10.2
eV of
energy, it moves to level 2. What typically happens next?

Hint M.1

Study Section 5.3.

ANSWER:

A different electron drops into level 1, since it is now
unoccupied. The electron returns to level 1 by
emitting an ultraviolet photon with 10.2 eV of energy. The
electron jumps to level 3 as soon as it absorbs any additional energy. The
electron remains in level 2 until it absorbs an additional 10.2 eV of
energy.

Part N

No object produces a perfect thermal radiation spectrum,
but many
objects produce close approximations. Which of the following would NOT
produce a close approximation to a thermal radiation spectrum?

Hint N.1

Study Section 5.4.

ANSWER:

a star you a filament in a light bulb
hot thin (diffuse, nearly transparent) gas

Part O

Which of the following statements about thermal radiation
is always true?

Hint O.1

Study Section 5.4.

ANSWER:

All the light emitted by hot object has higher energy
than the light emitted by a cooler object. A hot object
produces more total infrared emission than a cooler object. A cold
object produces more total infrared and radio emission per unit surface
area than a hot object. A hot object emits
more radiation per unit surface area than a cool object.

Part P

Betelgeuse is the bright red star representing the left
shoulder
of the constellation Orion. All the following statements about
Betelgeuse are true. Which one can you infer from its red color?

Hint P.1

Study Sections 5.4 and 5.5.

ANSWER:

It is much more massive than the Sun. It is much brighter
than the Sun. Its surface is cooler than the surface
of the Sun. It is moving away from us.

Part Q

The planet Neptune is blue in color. How would you expect
the
spectrum of visible light from Neptune to be different from the visible
light spectrum of the Sun?

Hint Q.1

Study Sections 5.4 and 5.5.

ANSWER:

Neptune's spectrum would peak at a much longer wavelength
than the Sun's spectrum.
The two spectra would have similar shapes, except Neptune's spectrum
would be missing a big chunk of the red light that is present in the
Sun's spectrum.
There is simply no way to predict the answer to this question, since
planets and stars are made of such different things.
The two spectra would have similar shapes, except Neptune's spectrum
would be missing a big chunk of the blue light that is present in the
Sun's spectrum.

Part R

All of the following statements about the Sun's corona are
true. Which one explains why it is a source of X rays?

Hint R.1

Study Sections 5.4 and 5.5.

ANSWER:

The corona lies above the visible surface of the Sun. The
corona's structure is largely shaped by magnetic fields. The temperature of the corona's gas is some 1 to 2
million Kelvin. The corona's gas consists mostly of hydrogen and helium.

Part S

From laboratory measurements, we know that a particular
spectral
line formed by hydrogen appears at a wavelength of 486.1 nanometers
(nm). The spectrum of a particular star shows the same hydrogen line
appearing at a wavelength of 486.0 nm. What can we conclude?

Hint S.1

Study Sections 5.4 and 5.5.

ANSWER:

The star is getting colder. The star is moving
away from us. The star is getting hotter.
The star is moving toward us.

Part T

Suppose that Star X and Star Y both have redshifts, but
Star X has a larger redshift than Star Y. What can you
conclude?

Hint T.1

Study Section 5.5.

ANSWER:

Star X is moving away from us faster
than Star Y. Star X is hotter than Star Y. Star X is coming
toward us faster than Star Y. Star Y is moving away from us faster
than Star X. Star X is moving away from us and Star Y is moving toward
us.

Part U

If we observe one edge of a planet to be redshifted and the
opposite edge to be blueshifted, what can we conclude about the planet?

Hint U.1

Study Section 5.5.

ANSWER:

The planet is rotating. We must
actually be observing moons orbiting the planet in opposite directions,
not the planet itself. The planet is in the process of falling apart. The
planet is in the process of formation.

Part V

Studying a spectrum from a star can tell us a lot. All of
the following statements are true except one. Which one?

Hint V.1

Consider all that you have learned about
light in Chapter 5.

ANSWER:

We can identify chemical elements present in the star by recognizing
patterns of spectral lines that correspond to particular chemicals. The total amount of light in the spectrum tells us
the star's radius.
Shifts in the wavelengths of spectral lines compared to the wavelengths
of those same lines measured in a laboratory on Earth can tell us the
star's speed toward or away from us.
The peak of the star's thermal emission tells us its temperature:
hotter stars peak at shorter (bluer) wavelengths.

Part W

Suppose that two stars are identical in every way --- for
example, same distance, same mass, same temperature, same chemical
composition, and same speed relative to Earth --- except that one star
rotates faster than the other. Spectroscopically, how could you tell
the stars apart?

Hint W.1

Consider all that you have learned about
light in Chapter 5.

ANSWER:

The faster rotating star will have an emission line spectrum while the
slower rotating star will have an absorption line spectrum.
The peak of thermal emission will be at a shorter wavelength for the
faster rotating star than for the slower rotating star. The faster rotating star has wider spectral lines
than the slower rotating star. There is no way to tell the stars
apart spectroscopically, because their spectra will be identical.